During the winter of 1804/05, the men of the Corps of Discovery take
part in Indian hunting parties and social events, while providing rudimentary
medical care to the Indians and the services of their blacksmith, John
Shields. They also speak with British and French-Canadian fur traders
who are well established with the Indians. Lewis hires Toussaint Charbonneau
as an interpreter, and agrees that he can bring along his Shoshone wife,
Sacagawea, who has given birth in February to a baby boy, Jean Baptiste.
Lewis and Clark also select those who will travel to the Pacific and
those who will return to St. Louis with the keelboat.

Spring - Summer: On April 7, 1805, the Corps of Discovery (numbering
28 soldiers and 5 civilians) departs the Mandan villages in the two
pirogues and six canoes en route to the Pacific, while Corporal Richard
Warfington, six privates, one Arikara chief, and three civilians head
down the Missouri to St. Louis in the keelboat. After two months the
Expedition reaches the Great Falls of the Missouri River on 13 June.
Two months later the Corps of Discovery finally meet the Shoshone. At
a council with the Shoshone on August 17th, Sacagawea recognizes the
chief as her brother. The Shoshone supply the Expedition with horses
and a guide for the arduous trek across the Rocky Mountains along the
Lolo Trail to the Nez Perce village.

Fall - Winter: In late September the Expedition reaches the
Nez Perce village, where it holds a council with the tribal chiefs on
September 23rd. Anxious to get to the Pacific, the Corps of Discovery
departs the Nez Perce on October 7th and begins its final trek west
down the Clearwater, Snake, and Columbia Rivers to the ocean. On November
7th, the Expedition sights an inlet from the Pacific. Clark writes in
his journal, "Ocian in view! O! The joy!" As soon as they
arrive at the ocean, Lewis and Clark reconnoiter for a site to make
their winter quarters. Just south of present-day Astoria, Oregon, the
Corps of Discovery builds Fort Clatsop in honor of the local tribe.
The fort is complete on December 23rd.